1) Remus/Neville, Neville/Teddy. Neville takes Teddy under his wing at Hogwarts just as Remus had done for Neville.
2) Sirius/Harry/(Remus). Christmas at Grimmauld Place.
3) Draco/Teddy. Draco catches Teddy sneaking a drink at a family gathering and teaches him a lesson (dub-con OK but no non-con, please).
4) Charlie/Draco. Set during GOF, Charlie tames the one dragon in residence at Hogwarts.
5) Severus/various Slytherin students. One of the perks of being the Head of Slytherin House dates to the time of the founders. Severus finds he quite enjoys deflowering each of his little snakes.