If you listen to the video you'd pick up on two interesting facts.
1. they started dating 3 years ago when she was 15 and he was 20.
2. she has been trying to get pregnant for over a year, but they just now got engaged.
The mom in the video acts like they shouldn't get married, i'd think at this point she'd be relieved that they are. Besides, it could have just been my impression, but the do seem happy and in love, and have been living together for just over a year.