Did Tom Nijssen and Robert Seguso play the same sport professionally?
yes
Tom Nijssen
Tom Nijssen (born 1 October 1964 in Maastricht) is a former professional tennis player from the Netherlands.
Robert Seguso
Robert Arthur Seguso (born May 1, 1963) is a former professional tennis player from the United States.
 A doubles specialist, he won four Grand Slam men's doubles titles (two Wimbledon, one French Open and one US Open).
 He also won the men's doubles Gold Medal at the 1988 Olympic Games in Seoul, partnering Ken Flach.
 Seguso reached the World No. 1 doubles ranking in 1985.
 He won a total of 29 career doubles titles between 1984 and 1991.
1990 Belgian Indoor Championships – Doubles
Wally Masur and Tom Nijssen were the champions of the event when it last took place, in 1988.
 Neither of them participated in 1990.
<br>Emilio Sánchez and Slobodan Živojinović won the title, defeating Goran Ivanišević and Balázs Taróczy 7–5, 6–3, in the final. 1989 Lorraine Open – Doubles
Jaroslav Navrátil and Tom Nijssen were the defending champions but did not compete that year. 1992 Lyon Grand Prix – Doubles
Tom Nijssen and Cyril Suk were the defending champions, but lost in the semifinals this year. 1986 Tokyo Indoor – Doubles
Ken Flach and Robert Seguso were the defending champions, but Seguso did not participate this year.
 Flach partnered Paul Annacone, losing in the first round. 1992 US Open – Mixed Doubles
Manon Bollegraf and Tom Nijssen were the defending champions but only Nijssen competed that year with Helena Suková. 1989 French Open – Mixed Doubles
The Mixed Doubles tournament at the 1989 French Open was held from 29 May until 11 June 1989 on the outdoor clay courts at the Stade Roland Garros in Paris, France.
 Manon Bollegraf and Tom Nijssen won the title, defeating Horacio de la Peña and Arantxa Sánchez Vicario in the final. 1990 Stella Artois Indoor – Doubles
Jakob Hlasek and John McEnroe were the defending champions, but lost in the quarterfinals.
<br>Omar Camporese and Diego Nargiso won the title, defeating Tom Nijssen and Udo Riglewski 6–4, 6–4, in the final. 1988 Tokyo Indoor – Doubles
Broderick Dyke and Tom Nijssen were the defending champions, but Nijssen did not participate this year.
 Dyke partnered Kelly Evernden, losing in the first round.