Yes, you can buy several tests in the same order. Each person registers their own kit, gives informed consent and sees only their own results. Kits for children aged 3 or over must be registered by their parent or legal guardian.
This is also a useful way to plan follow-up testing: keeping a second kit at home allows you to repeat the analysis when you want to see how your microbiome has changed, provided you use it within 12 months of purchase and before its expiry date.