Trauma ~ The seme has a past where he was neglected from family-love since he had to live with his uncle. The uncle and his family didn't care for the seme, and since the seme wasn't living with his actual parents, he never fit in at school. Due to his genes, he also attracted a lot of women, though they were all women that were taken. Due to this, he would end up in fights and trouble, even though he wasn't the one who went to them, they came to him. He was neglected from true/real love.
Kid ~ the child is the uke's nephew - his current situation is similar to how the seme's past was, but the difference is that the child is loved
Hinadori wa Shiokaze ni Madoromu