BL manga with MCs as parents/guardians

Ezakike Shuu's parents left for Africa to fulfill a life long dream, leaving their children behind in the process. Shuu has been taking care of his brothers since then, but outsiders judge the children for growing up without parental guidance. Shuu is devoted to bringing joy into his brothers' lives and leaving them with happy memories. Everything changes when Shuu meets his homeroom teacher.
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• children are 15,15, and 11 years old
• twincest

A story about the adventures of two NY cops, Dee and Ryo. A few chapters in, Ryo adopts an adorable yet violent kid, who constantly attacks Dee (who fell in love with Ryo at first sight) in order to protect the chastity of his beloved guardian.
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• child is 10 years old (there are occasional flashforward chapters of him at various ages)
• another child (female), age 13, is also prevalent in the story and close to the main characters, almost like family

Sequel to "Fake"
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• child is 11 years old (there is also a flashforward chapter in which he is 17 or 18)

A cram school teacher who was dating his student broke it off right before graduation. Four years later his ex turns up again, saying that he needs a place to stay.
(ch 3 - 4)
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• child is a baby

Graduate student Asahi is left to watch over his young nephew while his sister is away on business, but he's tight on cash. While shopping he coincidentally bumps into his old friend, Nishino. After hearing about Asahi's situation, Nishino offers to help, so the three start living together. Everything goes fine, but Nishino's "skinship" starts to get a little too invasive.
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• child is 5 years old

Allen and Kanda are given a mission unlike all the others they have had: take care of two kids.
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• children are primary school age

A loan shark makes a woman in debt leave her family so that her boyfriend will have to pay back her loan. Knowing he doesn't have the money, the loan shark is expecting his intended target to repay him through other means.
(ch 3)
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• child starts in primary school

Spin-off of "Kuroneko Kareshi no Aishikata"
Duty-driven Jin Kakami gave up his first love in order to have an heir. Now divorced and living with his young son, Rio, Kakami also lives with Takamizawa, his servant and former love.
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• child is 4 - 6 years old

Sequel to "Fukigen Kareshi no Nadamekata"
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• child is 6 years old

Nearly two decades after being jumped by a friend who was recovering from a broken heart, Teru is informed that he has twin sons and needs to take responsibility. While waiting for the paternity test results, he lives with the two teens, one of which acts far friendlier than a son should.
(ch 5)
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• child is 17 years old
• 13 year age gap
• incest