BL manga with MCs as parents/guardians

A preschool teacher is attracted to the father of one of the kids: a handsome and much older man.
(ch 6)
•
• youngest child is pre-primary school

Haruhiko's friend is in a relationship... with a 12-year-old. He's to meet his lover's father (who is unaware of their relationship) for the first time, and asks Haruhiko to tag along to help break the ice. He ends up being forced to come to future meetings, and he and the young father soon end up developing feelings for one another.
• (at first)
• child starts at 12 years old
• 12 year age gap
• mild shotacon scenes with son and BF

Tetsuo's ex drops off their 14-year-old son, Haruka who wants to move in so that he can live closer to his friend (and crush), Tamaki. Now Tetsuo has to deal not only with his failing love life due to impotence, but also with a gay son and his genophobic crush, a man he barely knows that keeps making unwanted advances, and his unhelpful friend who doesn't seem to have any useful advice to offer.
•
• child is 14 years old
• 18 year age gap

Hisui's sister abandons her son, leaving her brother to raise him. He and his childhood friend and sort-of-but-not-really lover, Yuujirou, raise the child together.
•
• child starts as a baby

Spin-off of "Dekichatta Danshi"
Konno Wataru gets by day-to-day going to university and trying to fight off the advances of his butler, Azuma. One day her receives word that his sister was in a horrific car accident. Apparently his sister had given birth to a child, and while she remains unresponsive in the hospital, it is up to Wataru to watch over his young niece.
•
• child is a baby

Ikusa, is in charge of holding down the fort while his mother is busy or away. His younger brother, Mikado, has always been chasing after Ikusa, and when his advances finally start getting him somewhere, chaos ensues, and the whole family gets sucked into it.
•
• child is in primary school
• incest

The main couple is a high school student and the school nurse, but the last few chapters focus on his father and his secretary.
(ch 4 - 6)
•
• child is in high school

Akamine Kakeru seeks refuge from his abusive parents, and is taken in by Shouichi. He and his daughter are the first real family Kakeru has been a part of.
(ch 2)
•
• child is 10 months old
• 28 year age gap

Sequel to chapter 1 of "Everyday Smile"
(ch 5)
•
• child is 1 and a half years old
• 28 year age gap

Sequel to chapter 1 of "Everyday Smile"
•
• child is at least 1 and a half years old
• 28 year age gap