Inviting relative's family - questions

[rrrrv]

I am inviting a relative's family (him, his wife and 22 yr old daughter) for a visit of about 6 weeks this coming summer.

He is going to be sponsoring the trip.

Do I still need to fill the I-134 form, or just the invitation letter to the consulate and to my relative is enough? If I still need to fill the I-134, what other documents do I need to submit?

[immihelp]

If he is paying for the trip for himself and his family, you don't need to send I-134 form.

However, make sure that either he or you buy the visitors insurance for them from the U.S. based company before their arrival, available for instant purchase at https://www.insubuy.com