With all the problems barnabas has i don't think anyone should be romantically involved with him.Whoever he ends up with has a heap of problems to deal with for the rest of their lives.That said,the only people he could end up with would already have to know about his past and be comfortable with it and the trouble that will occasionally crop up,otherwise he'd be trying to hide his past and possible otherworldly problems that crop up from time to time from his mate and that could strain things.That leaves Angelique(strange choice considering all she's done to him,repentant or not)
,or Julia(deserves better to be honest,but would be barns best bet for a truly loving relationship with someone who loves him with all her heart)
.Of course he can pick someone else,but he's going to be paranoid about his past being discovered or a new occult enemy appearing out of the blue that could scare his wife and god alone knows what 'ol barny boy will do to protect his interests!