Frank is Shirlena's grandfather, although it is unknown which side he is from. He appears for a few seconds in "Speak English!!!" where he supposedly defecates in his wheelchair while Danny is taking care of him. He appears to be close to dying, as he is confined to a wheelchair and seems to have lost most of his marbles, considering he has been afflicted with Alzheimer's disease, and considering he needs to be taken care of in the first place.
In the past, due to his Alzheimer's, he once went missing from the house and got lost at K-Mart for 2 hours. His family didn't know where he was, and he didn't really know where he was either, and somehow he ended up at K-Mart. He was walking around, trying to find a door just to get out. The employees found him in the mousetrap section, taking his clothes off. A worker was yelling at him to get out of K-Mart while he had his pants around his ankles (since they probably didn't realize he had Alzheimer's and may have presumed that he was merely a pervert). He apparently was 'confused' and 'didn't know where he was'. Shirlena told this the day after it happened to Danny who instead of showing any sympathy towards him, burst out laughing and referred to him as 'an ass'.
Considering Shirlena is presumably around the same age as Danny (around 50), and Frank is Shirlena's grandfather, this would likely place Frank at the very least in his mid 80s, likely even older.