I don't know about "always", but yes, there's a strong rational element behind favouring friends and especially family, and in general others that you're more likely to interact with in the future. For one thing, I'd think confidence that you have family members that will ensure your children will thrive even after you're gone gives peace of mind for most parents. And even if I never actually need help from family or friends of the nature I give them now, the regular act of providing assistance is an important part of what maintains good relationships, which we all know are pretty vital to mental health etc. I would say though that giving money is probably not generally the best way to achieve that end, and EA are primarily (solely?) about monetary donations.

Honestly I don't think there's any realistic way to decide in general whether giving assistance to person A vs person B is more "rational" or even more "effective", but it's good to at least be aware that some charities/NGOs/etc. are at least trustworthy and ensure a high % of donations do actively go towards providing help, rather being swallowed in marketing and admin budgets.