The ceremony of erusin ideally takes place with ten men present, seven aside from the witnesses and groom, and they may be relatives of the couple (they are not there to witness legally, only colloquially/ceremonially). “Ideally” is the view of Rambam and the consensus, this is a desideratum rather than a requirement, in contrast to She’iltot to Chayyei Sarah, who seemed to think it a necessity.
(Se’ifim 10-12 discuss what to do if the berachah was not recited at the kiddushin at all, a circumstance unlikely enough in our times—and where his consideration is whether it can be said at the much later nisu’in, which is completely not true in our times—that I am going to leave it undiscussed.)
The berachah on kiddushin, a vehicle to consider the mitzvah component of marriage, to think about what we are celebrating with this stage of marriage, a key component of the sanctity of the Jewish people.
