When there are only two of you and you want to take a picture with both of you in it, there are 2 standard ways to do it.

Option 1: Cram close together and one of you takes the picture by extending your arm out as far as you can. Using this method, you can't really get more than 2 head in the photo and if you're not careful, you might even get a nice view of your arm.

Option 2: Find a stranger to take your picture. This only works if there are other people around and will probably give you a better looking picture, especially if there is a background or something around you you want to have in the photo.
The downside is you have to be careful who you ask to take the picture. You've got to ask someone you know you can outrun, just in case they try to steal your camera. A while ago, some friends and I decided that an middle-aged woman was the safest choice. And if using a non-digital camera, you can't ask any sneaky looking folks because there was always the chance that whoever took the picture cut off your heads in the frame, giving you a nice picture of your shoes or something useless.