Birthdate issues.

My partner wishes to immigrate from the United States to the UK so that we can engage in a Civil Partnership, we have the visa form that allows us to apply for a partnership on his entry into the UK, but there is just one problem.

We have all the relevant information and paperwork at hand except for one apparently vital detail; my partner is not aware of his father's birth-date, there are reasons for this. Suffice it to say, his mother and his father were not married, and he knows very little of his father.

Without this information, we've hit a roadblock and we have no real means of acquiring this information so that we may continue, and both he and I would imagine that if we were to leave that blank or even explain the situation on the form, he'd be refused point-blank.

Could anyone advise?

(I'm sorry to have created an account just to ask this, but after having pored over countless FAQs and sources of information and having not found anything conclusive, I figured this would be the next logical step before phoning the embassy and/or trying to get hold of an immigration officer.)

It's not uncommon for applicants in certain parts of the 3rd World to be unable to give exact dates of birth for their parents, and it doesn't disadvantage their applications. I therefore can't imagine that failure to supply his father's dob is going to make much difference to your partner. If his identity is not in doubt and his own country has issued him with a passport, the info about his antecedents is of limited importance.
If he just sticks "not known" in the relevant box, he can offer an explanation if required. He could supply a notarised copy of his birth certificate to make sure.

That was very, very helpful and reassuring, thank you! We'll do what you advised too, just to be sure.