from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
NATURAL AFFECTION. The affection which a husband, a father, a brother, or
other near relative, naturally feels towards those who are so nearly allied
to him, sometimes supplies the place of a valuable consideration in
contracts; and natural affection is a good consideration in a deed For
example, if a father should covenant without any other consideration to
stand seised to the use of his child, the naming him to be of kin implies
the consideration of natural affection, whereupon such use will arise.
Carth. 138 Dane's Ab. Index, h.t.