To start, I suggested that Mathew do all the talking. We female-types tend to be overly concerned about upsetting feelings, and this was no time to worry about feelings. Their possible future son-in-law needed to be put on notice that his prospective father-in-law was prepared to protect his daughter.
You see, a young man should fear his girlfriend's father, not try to be his buddy. He's supposed to spend the rest of his life worried about pissing off his father-in-law over the way he treats his daughter. That's the way it was in the old days, and a healthy fear and respect is still needed today.
My suggestion to Mathew was this: Sit with him and hear him out. Then, say, βDuring the next 5 years before you propose, this is what I'm expecting from you β no shacking up. No knocking her up. Come back in 5 years, after I see how you treat my daughter, and ask for my approval. She was a teenage girl just a handful of years ago, and neither of you are prepared to make this decision right now. It's romantic, and exciting and adorable, but it's not realistic, and I don't support it. And, believe me, you don't want to live in a world without my support.β
If you too are the father of a young woman interested in getting engaged, take care of business, dad! Spell out your expectations then watch how her boyfriend responds. It will tell you all you need to know about the quality of man she is hoping to marry.