You may have tried to tickle your Mum's feet a couple of times only to incur her annoyance. If she has a sister, why not see if you can tickle her instead!
The best time to attempt a tickle is when there is nobody else around, say when you're visiting her house.
It's best if she is already barefoot, but nylons can be even more ticklish to the touch.
You will need to raise the subject either by introducing it at a point in the conversation or perhaps enquire more directly, as in, " Are your feet ticklish?"
You might get a funny or disapproving look and be told to behave. However if she is strangely silent or looks hesitant, perhaps blushes slightly, then you may have uncovered her little ticklish secret !
She may even mumble something like, "...actually my feet are very sensitive..." or " ...if anyone touches my feet I go crazy..."
Your best bet here is to just go for broke and suggest you just try a little tickle to see!
At this stage the reply is likely to be, " Ok then, just for a second, but no more...I know how ticklish my feet can be..."
Once her feet are in your lap, you should begin with the lightest of fingertip touches across the top of the toepads and gently caressing the arches, especially under the ball of the big toe.
In this way, you are almost certain to get a response straightaway just in case she attempts to remove her feet too soon.
The lightest of teasing, feathery touches which build up anticipation are always the most ticklish at the start and she may even allow you a few moments longer with this method.
Once she is reassured, relaxed, and openly laughing out loud, you could try for some deeper fingertip exploration.
This will either lead to her pulling her feet away and saying, "that's enough now", or she will just double up with intense laughter - or both!
If you're lucky, she may really enjoy the experience and you are allowed to continue or it might be all over in a few seconds, it's all up to how skilful you are.
An experienced tickler can actually make a novice ticklee want to be tickled as they have just discovered a whole new pleasure experience.
Your aunt may be that person - and you could try a second attempt later and see what reaction you get. You never know, she might allow you to tickle for a longer period of time!