theyneedto followevery technique that was given to them by thier parents 间 为什么要加上to

习惯用法：

give sb sth :给某人(sb)某物(sth)

give sth to sb:把某物(sth)给某人(sb)

这里是把technique给了 them

所以要用give sth to sb的形式

固定词组：sth. be given to sb.
某物被给予某人

因为that was given to them是用被动态修饰technique。如果是主动态就是give every technique to them。把every technique提前后，其他成分不变，所以to还留在give后面