Our mature foster mother allows us to engage in sexual activities while she watches

Our foster mother has always been a bit of a wildcard. She's always been a little too interested in our private business, but we never thought she'd take it this far. The other day, she caught us fooling around and instead of scolding us, she joined in. It was a little weird at first, but we soon got over it and started enjoying ourselves. The things she taught us were mind-blowing. We never knew sex could be so much fun. Now, every time we're alone with her, we can't help but get a little naughty. She loves watching us and joining in whenever she can. It's a bit strange, but it's definitely exciting. And who knows, maybe one day, she'll let us watch her too.