PMN Caecilia & TheSerif
"PMN Caecilia by Peter Matthias Noordzij (released by Adobe in 1991) predates Luc(as) de Groot’s Thesis by some 3 years (originally released under the FontFont banner in 1994), but the production of Thesis started in 1989, so it’s quite possible they were developped almost simultaneously.
Peter Matthias produced the preliminary sketches for his PMN Caecilia typeface during his third year of study in 1983. Perhaps Luc(as) was looking over his shoulder in class? Or was it the other way round? ;) The actual type family was designed in 1990 and named for his wife. Which is sweet.
I think the fact they seem pretty similar is because they’re both by very talented, very Dutch ;) type designers who are about the same age and studied at the same school, the Koninklijke Academie van Beeldende Kunsten in The Hague, with the same tutor, Gerrit Noordzij, who is Peter-Matthias’ father. And both typefaces were designed according to the same principle of the broad-nibbed pen.
You can find more info about the genesis of Thesis at Lucasfonts > The LF Font Families > Thesis Classic > Info & Samples. The most interesting part of the creation, its original design under the name Parenthesis as the “corporate” typeface for the ministerie van Verkeer en Waterstaat, is not included anymore, sadly enough."