Please help me understand?

My sister accused my 71 yr old dad of molesting her 5 yr old daughter..(my sister has a history of being mental) I found out when they went to my sister house to follow up, rachelle indeed say it was her grandfather who molested her(my sister more than likely coached her into saying it) my father has been nothing but a great dad to us...he even helped me raise my daughter for the first 5 years of her life along with my late mom's help..my daughter is now 11 and is resenting my sister for saying this about her grandpa..I found out that DCF does not have enough evidence other than what my 5 yr old niece said. My dad is hiring a criminal lawyer tomorrow, just in case...DCF said my dad should not live with me...do they have a right to say that and pursue it? I want my dad to live with me as i know he is innocent...I have an 11 yr old daughter and 3 yr old son and my dad is a great papa to them