I wouldn't use parents, siblings, cousins, grandparents or in-laws. The spouse of a second cousin could be used I'd guess but really you should just ask people near you. Get to know a few of your neighbors. Host a Halloween and/or Christmas neighborhood party or attend one to get to know the people around you. Our neighborhood has 4 or 5 houses who host holiday parties for the neighborhood and it was a great way to meet people. While most of the people don't socialize often (aside from a friendly wave to each other) this is a way to bring everyone together. We attended 2 of these when we moved here and I asked 1 person about the questionnaire and by the end of the night we had 20 who said they would sign one for us.
btw be prepared to send in a 'complete' drivers extract from your prior state's DMV to help speed up the process. We lived here in DE for 2 years before sending our paperwork in and this delayed us a bit when the investigator called and requested the abstract. I've been told this is now standard practice for people living here for less then 5 years.