I’m looking for novels where the mc has such an affinity with people that the strangers he/she met turn into friends -> family -> doting family. I want novels where the future older/younger ‘brothers and sisters’ were never interested in him/her romantically. There has to be more than just 1 stranger turn doting sibling in the novel It would be good if it was a an adventure/cultivation/isekai type novel but its fine if it isn’t.
The anime Ouran Highschool Host Club had that sort of troupe going for it I think. How about Muyoku no Seijo wa Okane ni Tokimeku? I think it meets your requirements...whatever they are. Kenkyo, Kenjitsu o Motto ni Ikite Orimasu too more or less. Yea, this is probably the one you're looking for. And also Observation Record of a Self-proclaimed Villainess’ Fiance maybe. Every side character here just wants to protect the FL. Try the second one. I think you'll like it.