Related in what sense? Are you sure they have the same genes in them coding the enzyme? Have you done background study of the same? Get the specific gene sequences from databases and do a nucleotide match. If you happen to find similarity, then proceed with the PCR using the same primers.
Hi. I don't think so. It seems that there is a lot of variation between nucleotides and aminoacids sequences in these genes. Check this paper: Opossum carboxylesterases: Sequences, phylogeny and evidence for CES gene duplication events predating the marsupial-eutherian common ancestor