How to conceive twins<br>Recognize that only about 3% of births result in multiple babies. Twins are not the norm when it comes to childbirth. While some things raise your chances of having twins (or other multiples, like triplets) slightly, it's a good idea to expect just 1 baby and be pleasantly surprised if you end with 2 or more.
Twins are less likely than triplets.
The context states noting about the likelihood of triplets so we have no way of knowing. I think the system gets messed up because it does state that you can raise the chances but it doesn't say what's more likely 
( z1 have-degree :ARG1 ( z2 twin ) :ARG2 ( z3 likely :ARG1 z2 ) :ARG3 ( z4 less ) :ARG4 ( z5 triplet ) )