If there is no minyan do you Sheva brochos and situation if there is no new person.
If there is no minyan, one does not recite all of the Sheva Berachos, but if there are three men the Asher Bara blessing (the last of the seven) is recited.
Some also say the Devay Haser introduction with three, and this can be done.
See Even HaEzer 62:7.
For the matter of Sheva Berachos without “new faces,” please see here. Although one should ensure that there are Panim Chadashos, some recite the Berachos even in the absence (as noted from the Aruch HaShulchan), provided there is some special feature of the event.