"I have a/an X" does not necessarily mean that I have exactly one X, it just means that I have one or more.
Suppose someone was looking for a ride home, and he asked, "Do you have a car?" If you own two cars, you wouldn't say, "No". You probably wouldn't even find it necessary to say, "I have two cars". You'd just say "Yes". (Well, unless you're looking for an excuse to not give him a ride.)
Suppose your local school announced they were having a "father/daughter dance", and said, "This is open to any man who has a daughter in this school." If you have two daughters, would you conclude that you were not welcome? Almost certainly not.
Or to take it a step further, if someone asked, "Do you have a daughter?", and in fact you have one daughter and one son, would you say, "No, I don't?" Probably not. Or if someone asked, "Do you own a cell phone?", would you say "no" because you own a cell phone and you own a laptop computer and you own a car and you own six pairs of underwear, etc? Normally, asking if you "have X" doesn't imply "and nothing else". If you want to specify "and nothing else", you normally need to add some words, like "only" or "just one". Like if someone asked me, "Do you have only one daughter?", I would answer, "No, I have two." I might also say that I have two sons as well, if the context of the question implied that the person was asking if I had only daughters.
All that said, there may be contexts where it would be understood to mean exactly one. I can't think of one, but I can think of a somewhat similar example. Suppose someone said, "In this country it is illegal for anyone under 18 to buy alcohol." If in fact the law said it is illegal for anyone under 21 to buy alcohol, there's a sense in which the statement is technically accurate: Yes, it is illegal for anyone under 18 to buy alcohol. But it is also illegal for anyone between 18 and 21 to buy alcohol. But as worded the sentence is very misleading. It implies that anyone over 18 can buy alcohol, without actually saying that.
I suppose if someone said, "We are holding a conference for parents of girls being raised without any brother or sisters, only children who are girls. You sir, do you have a daughter?" Clearly then he means exactly one, but this example is highly contrived.
"I'm partial to..." generally is used in the context of making a decision. It's equivalent to saying: "I'm biased towards (choice A)".
It can also be used for more general expressions of preference:
Friends is a good show, but I'm partial to Seinfeld.
The reason that it would be a joke in the first example is that using such formal, emotionless terminology about something that the speaker is supposedly very passionate about (their husband) is ironic.
Best Answer
'Why, yes' seems to be an idiomatic expression, used to add emphasis to a response. The exclamation 'why' can also be used at the beginning of other sentences to express surprise, lack of patience, anger, etc.
This might help: http://forum.wordreference.com/showthread.php?t=1449759 http://www.oxfordlearnersdictionaries.com/definition/english/why_2