Bowls Dunedin was formed in 1907 and this was the first time a brother and sister had won separate provincial titles on the same day.
The ''red letter'' performance came earlier this month when the men's and women's finals were held on the Taieri green.
Crawford (53), a compliance officer with Inland Revenue in Dunedin, beat Lyn Rance (Green Island) 21-15 in the women's final.
Webster (57), a Dunedin plumber, beat former international Ken Walker (Taieri) 21-18 in the men's final.
It has been a good season for Crawford, who won the New Zealand pairs title in January.
She has played bowls for 30 years and this month's singles was her 21st Bowls Dunedin title.
Crawford won her title in the morning on the Taieri green and watched nervously on the sidelines when her brother played the final.
''I was so thrilled for Ray,'' Crawford said.
''I was just as nervous watching his game as playing my own.''
Webster was a top indoor bowler and has won 15 Otago titles with the small bowls.
He won a South Island title in 1981 and a New Zealand pairs title in 1994, and represented New Zealand against Australia in 1987.
Webster, who joined his sister at the St Clair Bowling Club three years ago, regarded himself as a rank outsider when he played Robbie Thomson (Fairfield) in the semifinal.
Thomson is an experienced outdoor bowler and has won 14 Bowls Dunedin titles.
''I didn't give myself a chance when I played Ken Walker in the final,'' Webster said.
This was understandable, because Walker has won 31 Bowls Dunedin titles and has represented New Zealand at World Bowls.
Walker plays with aggression and attempted to upset Webster with drives and upshots.
Webster used his indoor bowls experience and just concentrated on draw bowls.
When Walker drove out bowls, he put his next bowl back on the head.
Walker is an entertainer and attempts to upset opponents with his antics on the green.
''I can sledge as good as he can,'' Webster said.
''He tried it on me and it backfired for him.''
Webster retained his composure throughout the game.
''It's unbelievable for a third-year bowler to win the singles title. It would have got good odds on the TAB,'' he quipped.
Crawford keeps all her championship medals in a box and will probably need a bigger one now.
Webster's son Phillip (28) is a fifth-year bowler with the St Clair club and his brother Harley (63) also plays for the club.
A sister, Marybell Ross, plays bowls on the Queensland Sunshine Coast.
