The decanal groups (tri, tetra, penta ...) are saturated fatty aldehydes and a n-alkanal and do not belong to the class of phenylpropanoids.
Tridecanal is a saturated fatty aldehyde with molecular formula C13H26O
Tetradecanal is a long-chain fatty aldehyde that is tetradecane in which two hydrogens attached to a terminal carbon are replaced by an oxo group. it has the molecular formula C14H28O
Pentadecanal is a long-chain fatty aldehyde that is pentadecane carrying an oxo substituent at position 1. It is a component of essential oils from plants with molecular formula C15H30O .
It means that, these groups of organic compounds has an aldehyde functional group.