Lots of good advice in this thread. Thank you. I had no idea that it was as common for a man to change his name as it is.

1. You're not just divorcing your father, but generations of family on his side.
That's a fair point. The thing is, I don't know any of my father's family except his sister (my aunt). I can probably count on one hand the number of times I've spoken to her in my life. And both his parents are dead. So it's not like I have much of a family connection there, or a group of people who would be upset. There's really no family there to 'divorce'.

2. Name changes don't look good on credit reports or background checks.
Another valid point. I have extremely good credit and try very hard to keep it that way. I'll check into it and see if there's some kind of industry standard on how it affects credit (i.e. does it drop a credit score by X number of points). Thankfully, with background checks, I really don't have to worry about that. The only reason I'd be submitting to one is for firearms purchases, but having a CHL exempts me from that requirement. And hopefully any other reason I might have for a background check, it would only possibly delay the result. Not disqualify me from anything (although I can't imagine that I'd want to be doing anything that requires one).

3. When a man changes his name, he ends up having to explain it to everybody he ever knew. While your intention may have been to distance yourself from the past, now you have to rehash it again and again.
This is the one that I sort of dread. Everyone will undoubtedly want to know why I changed my name. And while I have no problems explaining it to the people in my life who are important, there are a lot of people for whom it's simply none of their business. They don't need to know anything about my family situation. I'll just have to prepare a brief standard reply that isn't rude but basically relays to them that it's personal. And that it's carrying on a family name that was at its end.

If you care about your relationship with your brothers, tell them what you plan to do before you do it. You don't need their approval, but it would be a nice gesture. Also, when surprised, people often react negatively to something that they would look on favorably if it where explained to them before hand.
I've been debating on whether to do that or not. I called my mother this morning to talk to her about this and get her opinion. Knowing how judgmental my brothers can sometimes be (isn't that what brothers are for?), it might be best to just let them know afterward so that there's no room for debate on the subject; it will be over and done with already. My mother and I are on the same page as to how to respond to them about it. Mainly focusing on the angle that this carries on the Kilpatrick name and honors my grandfather (who was our de facto father figure when we were growing up), which is surely something that they would understand. They loved and respected him too. I think whatever anger or shock they feel at first would be mitigated by the sentiment of honoring him.

Anyway, one other dilemma I've been having is this: I am a twin. My father is a "junior" and wanted his first born son to be a "third". But nature played a cruel joke on him and gave him twin sons. My parents figured it would be unfair to name one son with the same name of the father and the other with something else. Instead, my father got to pick the name for the eldest twin and my mother named the youngest twin. So my twin brother, being the eldest, got my father's middle name as well as his last name. My mother chose my first and middle names to sound "Scotch-Irish" as she puts it. So my middle name is Patrick, since the Kilpatrick name was to be no more. And now that I'm going to go with the Kilpatrick surname, it seems superfluous to have the middle name Patrick.

I asked my mother what she thought. She had an interesting idea. My grandfather, who I'm trying to honor here, was always known as "Pat", since his first and middle names were kind of strange. They just gave him a nickname from part of his surname. So I could keep Patrick as a middle name for that reason. Or, her other suggestion was to change my middle name to the Gaelic spelling of the name, Padraig. That way it's still essentially the same middle name I've always had, but doesn't look like a redundancy with my new surname. I kind of like that idea, so I will probably do that.

She also suggested that I could pick an entirely new middle name, but I'd rather not. My goal isn't to create a new name out of thin air, but for it to be meaningful from the family names. I may have to look back in the Kilpatrick family history and see if there are names there that I might consider as well. *shrug*