To apply for a 143 or 870 visa you need sponsorship as follows: "To be eligible for the visa, a parent must be the biological parent, legal parent (including adoptive parent), step-parent or parent in-law of the sponsor, who must be an Australian citizen, Australian permanent resident, or eligible New Zealand citizen."
My daughter lives in Oz with an Australian citizen partner and they have a baby together. Would he be eligible to sponsor us for the above visas or do they need to be married for us to class as a Parent in Law?