Lock Up Boy
Tonari Ni Sunderu Neko No Koto
Cousins getting it on they have a 7 year gap.
Soukyoku (MEGU Iroha)
One word: twincest. Not really into that, will probably stil ok read. Bros one younger twin is down, older twin is like wtf. The relationship is strained for five years then then younger one proposes a wager.
Not Equal
Odd story. Guy falls into a wormhole while visiting his estranged father. Goes back 22 years and his 14 year old future father falls in love with him and they bang. He comes back to the future and is like oh that's why my dad was acting like that, but like I love him. They both are down, but like its taboo ya know
Rakuda Tsukai To Ouji No Yoru