Martial arts student a bit annoyed because I didn't go to his wedding?

He was a good student for three years and progressed well with me as his teacher. In the third year, he met a girl, who briefly was my student too, and they eventually got married and this year had a baby too.

In january this year he said he would maybe have to come to private lessons every three weeks instead of weekly, but stopped coming altogether. I remained in contact via email every so often, wished him well. He invited me to the wedding but I explained my wife may be on holiday so she wouldn't go, and in the end my mum decided to catch a late flight on the day of the wedding so I had to take her to the airport in another city on the same day!

I had about five days notice of this, apologised profusely, but apparently he got annoyed because others didn't go to the wedding, including his best friend from school.

I have students come to lessons from much further away than he lives now, so he just moved on. I don't see much point in staying in contact, and it's like once you leave facebook, people don't take an interest anyway!

I do wish him well, but wonder do other teachers keep students more as students? Because many regard me as their friend also, and whilst I keep a distance, I don't want them thinking I'm too standoffish.

Should i just not bother writing him again, and just leave it now?