How to reduce a pattern size

Are there any tips/rules for changing pattern size?

I am knitting a sweater for my husband and would like to also knit the same sweater for my children and me. Sizes would range from 18 months, 8 years, and large and extra large (I have the XL) patterns.

Any thoughts?

Thanks,
Heidi

What type of sweater is it? Do you have a link to the pattern?

A raglan would be easy to resize, but a seamed, set in sleeve type sweater might be harder.

You might be able to find similar shaped or design type sweaters in the appropriate sizes. Done in the same yarn, they will look matched.