I was inspired by this post, but I thought there might be other options for Game of Thrones byler!au
So, Will is one of the House Stark:
he likes the cold
his canon abilities are quite similar to those of wargs (people with the ability to enter the minds of animals and perceive the world through their senses and even control their actions), which are common among the Starks (in the books, all six of Ned Stark's children were wargs) and may be related to the powers of the Night King, like Will's abilities are linked to Vecna?
so Vecna could be a version of the Night King, turning people into his soldiers and raising the dead (and Mind Flayer could be one of the old gods, or maybe even older... well, it's up to you-
Mike could be a knight of the House Baratheon:
his dark curly hair reminds me of Lyonel Baratheon
he has taken a heart as his personal sygil (just like Stannis Baratheon)
he and Will were raised together in the Vale of Arryn like Robert and Ned, but Michael fell in love not with William's sister, but with William himself-
other options for Mike: a knight who belongs to one of the Lordly Houses whose coats of arms have hearts (Staedmon, Corbray)
bonus: Mike the Brave, a knight of House Wylde (because that house's sygil is literally a blue swirl on a yellow background 🌀☀️)