Ok, so you have a business entity organized/incorporated under US law with three shareholders/partners/owners. You are one of the three owners and the two others are resident abroad. You're assuming that jurisdiction is in the US and your defendandants are the two other partners, not the business entity. To me, it looks like this assumption is correct but I don't know the details of your case.
In this case, it will likely not be possible to use domestic process service; However, since international process service tends to be a dark art that is associated with a lot of red tape, you should first try to figure if you can use domestic service after all.
Options for domestic service include:
a) Service while travelling: If your defendants travel to the US, you can serve them personally as long as they are on US soil. Residency doesn't matter. You just need to get a US process server to ambush them whereever they are in the US.
b) Service on service agent: If your defendants have arranged a US-based service agent who is allowed to be served on their behalf, you can serve the service agent. (I'm mentioning this for the sake of completeness, because international contracts sometimes include a clause that requires the parties to appoint a domestic service agent just in case there will be a lawsuit.)
c) Service on subsidiary, Service on legal counsel: There have been cases where a US court decided that service on 1) a lawyer who used to represent the respondant in the past or 2) service on a subsidiary of the respondant is sufficient. I would be careful with these options because this looks like making up a service authorisation that doesn't exist.
If none of the above is available to you, you will have to serve process abroad. (Nota Bene: This doesn't mean that you have to exhaust your options for domestic service before intl service is allowed.) International process service is quite different from domestic service; In many cases, it involves some red tape, costs more than domestic service and it is much slower. In most cases, you are not allowed to hire a process server directly as this would (in most cases) be considered a violation of the Hague service convention, a violation of the destination country's national sovereignty and/or assumption of powers without authority.
The exact procedure varies for serving abroad varies heavily between countries; For further reading, I recommend this blog: https://www.haguelawblog.com/
If you tell me in which country you need to have your documents served, I may also be able to tell you more about service in that country.