I've left off the ones on AO3 with tags like "Meeting the Parents" and "Danny 'Danno' Williams' Family," so if you haven't explored those, you should :)
Respect Your Elders (http://archiveofourown.org/works/240110) by leupagus in which Danny's grandmother is visiting
Mission 'Secure Danno's Affections' (http://archiveofourown.org/works/274987) by ellievolia and sirona in which they don't meet but Steve talks to Danny's family on the phone
Our Story Was Not Told (http://h50-exchange.livejournal.com/18485.html) by andrealyn has Steve unexpectedly meeting a member of Danny's family
Familiar Enemies (http://silmanumenel.livejournal.com/1063.html) by silmanumenel is a bit of a stretch but Danny's family is, um, involved?
no subject
Respect Your Elders (http://archiveofourown.org/works/240110) by leupagus in which Danny's grandmother is visiting
Mission 'Secure Danno's Affections' (http://archiveofourown.org/works/274987) by ellievolia and sirona in which they don't meet but Steve talks to Danny's family on the phone
Our Story Was Not Told (http://h50-exchange.livejournal.com/18485.html) by
Familiar Enemies (http://silmanumenel.livejournal.com/1063.html) by