There is an easy way to test for ticks -- drag a white sheet across an area where you think there may be ticks. But, make sure that you spray your shoes, socks and clothing with Permethrin before you go out.
From everything that I have read, mice are a ticks favorite meal, so while it may be possible to get Lyme from fleas, if you have mice, it is probably more likely that it was from a tick bite.
We now have our yard sprayed for ticks every month from April to October and have not seen any ticks since we started spraying.
I hope that you and your brother are soon feeling better.