tl;dr- I'm talking about a guy falling for his best friend's younger sister and other similar stuff.

Need to have:

• Relationship between Character A and the family member/brother/sister of Friend B
• No yaoi or yuri

Nice to have:

• Character B is the one who brings them together
• A and family member of B end up together
• Completely scanlated series

long version:
I'm looking for any manga with a story that involves a character falling for the family member of a friend. I'm not sure if there's a better way to phrase it. Their relationship does not have to be the main focus of the manga, but there has to be solid evidence for it. Better if they do eventually become a couple.

Some examples below. They're the closest I can think of off the top of my head but I know there are other ones out there:

Kingyo Sou (Asuka and Masami via his brother)
Card Captor Sakura (Sakura and Yukito via her brother Touya)
FullMetal Alchemist (Al and May Chang via Edward// Roy and Riza via her father)
Tetsugaku Letra (Main Characters via MC's sister's school)
Friends the TV series (Monica and Chandler via Ross)

I'm up for re-reads and prefer completed series, but again, its not a requirement. No yuri or yaoi unless the story is an absolute masterpiece. I've tried the category tags but I haven't found a tag for what it is i'm looking for. Thanks in advance for anything you think of!

Maybe Hitorimi Haduki-san to.? Guy has a crush on classmate's older sister and she helps them get together.

Migawari Hakushaku no Bouken - they are the main couple. Guy falls in love with his best friend's sister.
Cherry Boy, That Girl - kind of. She ends up with her friend/boyfriend's cousin.
Banana Bread no Pudding - Guy likes his sister's friend and pretends to be gay so he can have a relationship with her (she wants to be the fake girlfriend of a gay man). It's a strange manga.
Futago - Guy falls in love with one sister at first but ends up liking the other.

Here's a few I can think of. Most are siblings/step-siblings, but the first is a bit different. It's my favourite manga. Anyway, so I would highly recommend the first manga if you haven't already read it:

Ai Hime - Ai to Himegoto
Dear Brother!
Marmalade Boy
Kedamono Kareshi