The “down syndrome boy” on 7th Heaven was a recurring character named David , played by actor Andrew Keegan? Actually, the better-known Down syndrome storyline involved the character Matt’s friend Jimmy in a special episode, not a long-running main cast member. If you mean the child actor or guest character from that storyline, the most likely answer is that he wasn’t a regular cast member and didn’t become a major public figure afterward. There isn’t a widely known public record of a dramatic later life tied specifically to a “Down syndrome boy” from the show.