Mako continued as a Triple Threat Triad member and ascended to the top, where virtues on brotherhood and family help solidify the Triple Threat Triads as the dominant gang in Republic City. He and Bolin managed to find and relocate his extended family from Ba Sing Se and moved them to Republic City where they now reside.
Bolin, being charismatic and adored by all, became a councilman who while very popular and seems to have the best interests for his city, is one of the most corrupt politicians. He lives luxuriously and is heavily involved in underground activities, and he is often at odds with his brother due to their differences in how they operate.
Some of their extended family follow Bolin and some Mako, effectively creating a feud in the family. They do however put their differences aside time to time whenever their grandmother steps into the picture.
Asami followed in her father’s footsteps, joined the Equalist. Amon’s secret was discovered and her father was killed in the process. She became the new leader of the Equalist movement after removing Amon from the picture with a temporary truce between herself, Mako and Bolin.
She managed to harness the power of spirit vines to fight benders on an equal footing. Although unable to remove bending, she is able to temporarily stun a person’s bending much more effectively than usual chi-blocking and has state-of-the-weaponry she and her Equalists use in their fight.
Korra was taken by the Red Lotus and hidden away from the world for much of her life, and has embraced the ideals of the Red Lotus and learned all sorts of advance variations of bending including flight, and combustion (Channelled through the tattoos on her palms instead of a third eye).
Jinora lost her bending and identity to Amon. She became depressed, angry had frequent nightmares about losing her bending. Unable to help his daughter, Tenzin under his mother’s advice sent her to Kyoshi Island to train with Suki, in hopes that she could rediscover herself or at the least, make her feel less vulnerable now that she can’t bend. She refuses to use the fans Kyoshi warriors use as it is a painful reminder of her severance from airbending. Suki also gifted Sokka’s sword to Jinora, hoping that it would help her the way it helped Sokka, giving him purpose as a regular human in a team of benders.
Kai acquired airbending, but instead of giving freedom and a new chance at life, it took away what little he had left. He was captured by the Dai Li and conscripted as an elite unit alongside other airbenders in the Earth Kingdom’s military. He wears a rock collar which is used by his Dai Li handlers to forcibly subdue him if he gets too rowdy or attempts to escape. His airbending is much more forceful,aggressive and offensive instead of what regular airbending is suppose to be.
Suyin raised Kuvira as her own and made Kuvira felt like a true part of her family, instead of just her prodigy, Baatar Sr made sure that his son walked his own path and wanted him to be his own person instead of a shadow of himself. Kuvira and Baatar Sr got married with full blessings from Suyin. Kuvira follows her saviour, her teacher and her mother footsteps and steps up to the deputy leader of Zaofu, while Baatar forged his own path and became a successful engineer and inventor in his own right.
Anyone making a story off of this AU, feel free to use these versions of these characters as you see fit.