Haha I didn't mean the age difference! I meant that he might be really close to his Calling.
I think the Warden is in his late 40s to mid-50s, though beards tend to age people and greying can happen prematurely, due to biology or stress--so he might be quite a bit younger. Whether he's close to his Calling or not, I don't know--could be, if he underwent the Joining pretty young. Either way, the Inquisitor is in his or her 20s to 30s, and the Warden's pretty much old enough to be his or her father. This is why many of us believe he's out as far as romance goes.
Going by who looks closest to the Inquisitor, age-wise, we've got Solas, Cullen, Scribe Girl (I really wish she had a name), Dorian, Cassandra, Vivienne, and Iron Bull. Almost all of the party. Any of them could be romances. I exclude Varric because of Bianca.