Form 3520 limit is 100K per house hold or per person?

That's a good question you ask.  I did some tax research on it it for you.  The answer I reached is that the IRS rules for the Form 3520 filing threshold are ultimately unclear, in the sense that you mean.

While there is a $100,000 limit per individual person (before Form 3520 is invoked), and the $100,000 limit can be breached, in aggregate, by the receipt of several smaller gifts made by related persons, totaling more than $100,000 to any one individual, it is uncertain if symmetry is preserved on the part of the recipient.  In other words, do the rules apply equally to multiple related receivers of a gift, or only to multiple related givers of the gift, for purposes of reaching the $100,000 filing limit?

Since this is somewhat of a true gray area, we can alternatively consider how US tax law would treat recipients of similar gifts, if the givers and the recipients were all US citizens, and also related to each other.  Under those conditions, the gift amounts would not aggregate together among the recipients, such that each person (husband, wife, child, uncle, cousin, brother, sister, etc.) could each receive less than the $14,000 domestic gift reporting limit amount, all from the same gift giver, without triggering a reporting requirement.

Using that as justification for taking a position, you could reasonably argue that no, you do not have to file Form 3520, if your father gives each of your family members $99k each.  However, a plausible argument could alternatively be made for the opposite conclusion (which I will not detail here, because the reasoning is too lengthy).

That said, you may want to file Form 3520 voluntarily, even if you do not absolutely have to, just to err on the side of safety and caution.  There is no actual tax due with Form 3520, and if you are talking about a reasonably straightforward gift of money or property from your father, then you only have to fill out Pages 1 and 6 (Part IV).  The form can be completed manually, and mailed.  Here are links to the form and the instructions:

https://www.irs.gov/pub/irs-pdf/f3520.pdf

https://www.irs.gov/pub/irs-pdf/i3520.pdf

What is the conclusion, then?  Well, ultimately that depends on what you decide to do, based on the above.  As a tax professional, I do not think that Form 3520 is absolutely necessary in your case; but as a client I would probably recommend that you still fill it out and file it anyway, simply as a matter of disclosure.  After all, there is no tax due with any Form 3520, and all it costs to file is a stamp and the time necessary to complete the form.  Fortunately, despite being 6 pages long, it's a relatively easy form, at least with respect to the beginning page, and Part IV on Page 6, which is all that you would need.

Thank you for asking this question.