Some lemon seeds i planted are poping up i so excited, my key limes haven't yet but i only planted them a week ago. One question i was wondering if grapefruit come true from seed or if they grow from seed at all?

Yes, a lot of grapefruits are nucellar or come true from seed, except perhaps for the more complex grapefruit or pummelo hybrids with mandarins.

My friend has a 17-year old grapefruit seedling, it has yet to bloom and fruit for him. I grafted Oro Blanco and Mato Buntan Pummelo to it yesterday.

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While most grapefruit come true from seed, those types with pigmented flesh but a white albedo (e.g., Thompson Seedless, Burgundy) don't; they produce seedlings which are 'Marsh Seedless' (white). Those pinks and reds which have at least some blush of pink in the albedo will come true-to-type.