-Super late response incoming.- I always assumed it to be Oldest: Splendy. Then Slendy. Then Trendy. And youngest as Offendy, since he is a sexual deviant, and usually people tend to grow out of it as they're older.
XD lol I thought Trendy was the oldest,Slendy is the second oldest (and the most responsible),Offendy is the Illegal numberith (3rd),and last but never least (unless you're talking about age,then yeah) Splendy!
and then,the distantly related half brother endy is in between Offendy and Splendy