Recently I (M30) was away on holiday with my wife (F30) and her family.

I was taking some time to myself relaxing in the sauna. About 5 minutes in I was joined by her sister (F21).

We chatted for a bit but I couldn’t stop checking her out in her little bikini. After a couple of minutes I could feel myself getting hard. I tried to find a position to hide it but with just a pair of small swimming trunks on I’m 99% sure she knew what was going on.

We chatted some more and she didn’t seem to mind. She still seemed pretty relaxed despite knowing what was happening

Afterwards I took myself off to the bathroom to cool off, but the sister was definitely looking at me differently that evening.