I've been seeing this guy for a month and he hinted at the beginning that he's about ready to settle down as he's turning 27 next month. On our first date he took me to see his older sister which I thought was kind of a serious gesture.
Now the problem is, I don't see him as much as I want to and it seems like he's always too busy to see me. He doesn't call when he says he will and I haven't been anywhere else with him besides his house and his sister's house.
Are some guys just too lax like that, or is this a sign that he's not really into me?
Besides our first ever phone call that lasted like 2 hours, all other conversations last less than 5 minutes.
I just need some insight and a little peace of mind.

Doesn't sound like much of a relationship. He really took you to his sister's house for your first date? If he's too busy to see you, and you guys really don't talk, and really don't go out he's sounding a lot like just a friend. Or even an acquaintance. If you feel like he's worth the effort, talk to him and see if the two of you can work things out. Otherwise it's time to move on.

You don't have much to show for a month, and I wouldn't worry about seeing a guy who doesn't show some attention, and wants to settle down after just meeting you. Hey he puts in no effort, maybe you shouldn't either.

If he said something about setling down this gives me two possible answers, both may be inaccurate.
A) He changed his mind about you and didn't feel like you were the one from him.
B) Might be that he took you to his sisters house to get you validated by her, and she might have told him something to change his mind.

B sounds more correct, but A is what it proberly is!

Get move on, find someone else. And when you find the right one, he will make sure you know, that you're his gal :) best of luck!