what do jem and scout learn about dill and his family situation?

Scout and Jem find that Dill spends their summers with his aunt Rachel in Maycomb. He is a sensitive child who strives for security. He initially seems to have a good relationship with his mother and stepfather, although Dill's any tall tales make it hard to establish the truth; as Scout says

...the biggest ones I ever heard

and there is evidence later that he runs away. Dil is clearly not as fortunate as Scout and Jem in their close relationship with their father, Atticus. He 'becomes' one of the Radley children during those summers and is witness to the teachings of Maycomb along with the other children.

With his Aunt Rachel, Dill and Jem spend the summer trying to reveal the secrets of Arthur "Boo" Radley by touching the house.