A mother with many children did not raise any of her many children. The brothers and sisters grew up in different orphanages and did not know how many there were in total…

My sister is looking for my younger brother Vasya, who was adopted when their mother was deprived of parental rights to four children. Other children learned about Vasya's existence only from the document about the apartment they were supposed to have. Does the mother herself remember about her son Vasya? And how many children did she have in total?