M 3/6/1965 adopted abt 2 yrs old, NC-brothers or sisters??

I found my birth family, now I'm helping my (adopted) brother find his. He was abt. 2 yrs old when placed (abt.1967?). The only story we have is "his parents were older and couldn't afford to keep him". If true, does he have brothers and sisters? Are they searching for him? Obviously he lived with them until placed in foster care. I was a baby and he was 4 when I was placed, he was the best brother, very caring and loving. Our adopted mom said that he would hold me, hold his hands to block light in my eyes, and was very protective of me, didn't want others to come near me, touch me, made sure their hands weren't dirty. (Other than that she is very closed mouth about any adoption info and doesn't answer questions.) I often wondered did he have a bio baby sister and they were seperated? Others?