I said before, Siren is a realm hopper and with that she's made some good friends in the different realms she's been to

Here's a basic summery of them all, or some of them;

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Bara Magna

Mata Nui
Siren and Mata Nui have almost a friendly sibling in law friendship, almost never argue though Mata Nui does have to scold Siren at times since she and his younger brother Makuta tend to get into trouble together that injure themselves

Ackar
Siren and Ackar are close as a Uncle and Niece friendship, Ackar teaches Siren of fighting melee as she prefers to use her mallot the most but will use a sword of necessary, also helping Siren learn to ride a Sand Stalker and drive a Dune Chariot as for Siren, riding a Sand Stalker is similar to riding a horse and driving a Dune Chariot is similar to driving an ATV mixed with a Go Kart

Kiina
Siren and Kiina are almost sisters at times, though having more of a somewhat in-law relationship of Kiina being married to Siren's boyfriend's sibling(their Non-binary), the two also act similar being they both have ADHD

Gresh
Siren at times sees Gresh as a sibling to replace her older brother, Gresh is protective of her but also cares a lot for her. He also let's Siren on his shoulders given Glatorian have giant heights which makes them taller than an Agori even when young

Berix
Siren and Berix love to work on mechanical things together as Siren sees him as a replacement for her younger brother
The two often get into trouble with pranks at times, but still close no matter what

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The Island of Mata Nui

Makuta
Makuta is the second most important person to Siren, her boyfriend being the first
The two are best friend's and at time often act like siblings more than Makuta is with his brother's
Makuta helps Siren of sudden energy boosts with her powers to help her keep a fight up when in trouble
Though the two get into trouble a lot and get scolded by Makuta's brother's, Mata Nui and Emiku, their still there for each other

Emiku
Siren isn't much close to Emiku, but does tolerate him for Makuta's sake
She slowly warms up to him when it comes to her mechanic like things she can't figure out
Emiku also manages to help Siren calm down of her moments of frustration given he had mainly used to do so with Makuta when they were younger which Siren appreciates

Roodaka
Siren often looks to Roodaka for helping her control her phyce and her sanity snaps seeing Roodaka has the most control over her Vortixx instincts
Siren looks up to her at times for her protecting nature and showing that even the most evil of people can change for the better like Roodaka has

The Turaga Metru
Siren is only close to Turaga Nokama and Turaga Nuju
Nokama let's Siren rant and vent to her of her frustration and issues regarding her mental health and Nokama helps her in whatever way she can
Nuju helps Siren learn things of Matoran and Toa cultures and appreciates Siren's dedication, quick learning and love to learn more, even helping her learn to write in Matoran

The Toa Mata/Nuva
Siren is closest of the Toa to Tahu, Gali, Kopoka, Lewa and Takanuva
Siren often likes to be on Tahu's shoulders when he allows it, enjoying the scenery from a Toa's height sense and often tries to help Tahu calm down from his anger without using her powers
Gali often takes Siren to the beaches of Ga-Wahi where she loves to swim and also look at all the reefs and fish in the ocean water, letting the girl use her shapeshifting to breath underwater with the Water Toa
Lewa let's Siren on his shoulders the most despite being the second shortest of the Toa Mata/Nuva with Gali being the shortest, and with his Mask's power and Toa powers let's the two fly without Siren using her powers to fly as they also make flower crowns for the others together
Kopoka is the only one who shows normal emotions around Siren, and with she doesn't see snow normally makes it snow at places for her to play with and see her smile but does have snowball fights with her when she throws one at him
Takanuva and Siren have a sibling like friendship, Takanuva tells Siren stories of his travels and when he was still a Matoran/Takua as Siren soaks up all the stories like a sponge

Certain Matoran
Siren is only known to be close of Matoran to Jaller who is Takanuva/Taku's best friend before he became a Toa and still is
Siren learns combat styles from the Matoran guards with his help and happily helps with missions he gets from Turaga Vakama

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The Night Dimension

NiGHTS
Siren is close to NiGHTS as the two often hang around in Nightopia/the Dream Side of the Night Dimension
Siren helps NiGHTS be a good spouse being married to Kiina as NiGHTS helps Siren feel more at ease in Nightopia

Reala
Reala is the most important person to Siren with him being her boyfriend
He treats Siren like a proper healthy relationship and accepts everything of her despite how her last relationships were and does what he can to see her happy and smile
He often takes Siren to see Cerberus/The Hell Hound given Siren is the only known person who can keep them calm and treats them well
Reala is worrying of Siren and when she lost a lot of blood once, donated his blood in a transfusion giving her genetics a shift for Nightmaren ones giving some Nightmaren abilities and her eyes to shift colors to her yellow with darker yellow cat slit pupils

Jackle the Mantle
Jackle and Siren are practically siblings feeding off their childish antics
Siren often helps Jackle with his Reality Dislocation from when Wizeman(their creator)was alive and caused the traumas to the Nightmarens especially Jackle
Jackle often helps cheer Siren up and also helped Siren practice her magic to where she is now
Siren has a deck of Jackle's extra Tarot Cards, which allow her to teleport another way by throwing them and where they stop or where Siren focuses enough she teleports in their place with the card in hand as the cards are also razor sharp to use as a weapon

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Extras;

Daniel Fortesque(MediEvil)
Siren met the undead skeleton knight when she first realm hopped and surprised Daniel of not being scared of his looks
After explaining what she was and some of her powers, the two remained close friends with Daniel and Siren having a sibling relationship where Daniel is a protective older and keeps her safe while the heroes at the Hall of Heroes he hangs around with help Siren learn more weapon skills

Al-Zalam(MediEvil Resurrection)
Siren and Al-Zalam have a sibling relationship as well but not as strong as her's with Daniel and Jackle
The two love the cause pranks mainly against some of the heroes in the hall of heroes and she loves to watch Al-Zalam use his powers as he puts on little magic shows for her to make her happy

Princess Kiya(MediEvil 2)
Siren is a bit wary of Kiya at times, but it's mainly her protective little sibling instincts for Kiya and Daniel are dating
She wants to make sure Daniel is happy and makes sure Kiya can do that
Though she is skeptical of her, Siren let's the two date as she slowly warms up to Kiya

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Yeah that's a lot, and there's a whole lot more trust me
This is just a few to get the idea of it all