@BigJMRA possibility is Deja Vu Ascendancy by AscendingAuthor.
Matches pretty well. Teen decides to commit suicide due to bullying and deja vu's during the suicide with an alternate self in a parallel universe. His body dies and his mind now shares space in his alternate's head. The combined force of their 2 minds starts having an effect on his body and lets him develop some unique abilities. Discovering the power of deja vu'ing and the resulting rollercoaster of his life (especially after he gets his first girlfriend), he gradually gets more and more powerful. While in the book he never actually gives his sister and GF powers, by the end of the book he has essentially become a god and offers his family and his GF's family immortality as well as telling them that if they want he will enable them to have his powers as well but gradually so they have time to adjust just like he did.
At one point he uses his abilities to win a lot of money at roulette in order for his family and GF's family to buy a mansion together for better security (the parents of both are aware of his abilities but not the source).
Eventually he does learn how to use his abilities to fly.
And the breaking into an office... well he does a lot of that at one point to gather evidence of government corruption due to the hassles his family gets from the government.