Parkinsons and Epilepsy

My Dad, now 80 years old has had PD for 10yrs+, he also has got Parkinsons Dementia too. Just recently he has started to have seizures, they are brought on through movement or exertion eg. like sitting up in bed, standing up.
He has been prescribed an Epilepsy drug, but at the moment is not doing much good. My mother, 76 yrs, is his sole carer and finds it hard to cope.
Does anyone out there as a carer have experience with seizures and PD?
My husband and his elder half brother have Parkinsons . His brother also has seizures. Not sure what drug he is taking for it . In fact he started having the seizures be being diagnosed with Parkinsons . I don't know if it is related .
Is there a link between epilepsy and Parkinsons? My mum was diagnosed wth epilepsy when she was going through the menopause and has just been diagnosed with parkinsons.