Did Mary have other children after Jesus?

Yes.  Mark 6:3 and Matthew (13:55–56) mention James, Joses, Jude and Simon as brothers of Jesus, the son of Mary and unnamed sisters.

Mark 3:31–32 tells about Jesus’ mother and brothers looking for Jesus. This incident tells us two things: firstly that Jesus’ adoptive father Joseph, is probably dead at this point. Something certainly the case at the cross when Jesus entrusts Mary’s care to John, something that could only be done with a widowed woman. Secondly the incident refers to Mary as their mother also, so these brothers of Jesus  are not children of supposed second wife of Joseph, but brothers who accompany their mother, Mary.