I have each type in a seperate Inlude file
Dont. Simple as that. If you need this sort of cyclic refferances, then put them in the same file simple as.Mind you it is stupid. Type A contains a Type B, which contains a Type A, which contains a Type B, which contains a Type A, which contains a Type B, which conatains a Type A, which etc (But I assume that it was just your example to show each type referanceing the other)