How can I set row height to two lines of text as a minimum, or more if cell contents requires it?

The row height should vary according to the font size. The entire worksheet will be in the same font size. Selecting the entire worksheet and increasing/decreasing font size should change the row height accordingly.

If a row contains nothing at all, then the row height should still be two lines. If a row contains a cell with a long entry that will wrap over more than two lines, then the row height should automatically expand to accommodate the text (to three lines or more).

I thought it was an easy one but so far I haven't been able to figure it out for myself or by searching this forum. Can anyone please help?