Yes, I've outright suggested to my sister and abusive sibling repeatedly over the years that they ought to consider therapy. At first, I even offered to pay for my abusive sibling, even though I was having flashbacks of his physical and sexual abuse of me.

These days whenever they rant to me or treat me like an unpaid therapist, I nip it in the bud and suggest they go to therapy. They just come up with excuses which boil down to "It's not a priority."