These are both series written by the same author (Reiji Miyajima) and both are airing seasons this year. Shiunji Family airs in the just beginning Spring season while the fourth season of Rent-a-Girlfriend airs in the Summer season. Check out the Crunchyroll article for additional information.

Synopsis for Rent-a-Girlfriend source manga from AniList:

Kinoshita Kazuya is a 20-year-old failure of a college student. He managed to kiss his girlfriend once, but was dumped after a month. “Ugh… Damn it. I never want to go through that again.”

Completely spiteful, Kazuya uses a certain method to date a girl. He goes to their meeting place and suddenly hears, “You’re Kazuya-kun, right?” A beautiful girl brushing her long, black hair behind her ear was there, smiling at him. Her name was Mizuhara Chizuru. Something real is born after just a single rental! A reckless rom-com filled with love and excitement is about to begin!

Synopsis for Shiunji Family Children from AniList:

Arata has never had a girlfriend, but he has 5 sisters and a brother. One day, his father reveals that he and his siblings aren’t related by blood! Now all bets are off, and Arata’s future promises to be rather nerve-wracking…