English to Spanish Law/Patents Law: Contract(s)

if both of the Settlors shall for the time being be under Disability, to pay or transfer to, or otherwise to apply for the benefit of, all or any one or more (to the exclusion of the other or others of them) of the class comprising
(a) the Settlors;
(b) the Senior Children;
(c) the Junior Children; and
(d) the Issue of the Senior Children and of the Junior Children

No entiendo qué son los Senior y Junior children, y mucho menos cómo decirlo en castellano.

Gracias por la ayuda.